Sonophotocatalytic degradation of methylene blue with magnetically separable Zn-Doped-CoFe2O4/α-Fe2O3 heterostructures

This work reports an approach of highly active sonophotocatalysts through the combined Zn-doping and heterojunction of CoFe2O4/α-Fe2O3 heterostructures. The novelty lies in the combined Zn-doping and α-Fe2O3 coupling strategy to tune the electronic structure and enhance charge separation of spinel-based magnetic nanocatalyst. A sol–gel auto-combustion method was used to synthesize Zn0.3Co0.7Fe2O4 nanoparticles with ~12% α-Fe2O3 content. The Zn-doping increased the magnetization saturation from ~65 to 86 emu/g and narrowed the optical bandgap from ~1.48 to 1.62 eV compared to undoped CoFe2O4, indicating a modified electronic structure. Under sonophotocatalysis, near complete methylene blue decomposition was achieved in 45 min for both catalysts, with a 30% synergistic effect observed. The Zn-doping also activated the semiconductor photocatalysis mechanism. The combined Zn-doping and heterojunction approach enables highly active sonophotocatalysts to effectively degrade dye pollutants and mitigate water pollution.